Electrophotographic developers are a dry developer in which toner components composed of materials containing a colorant and a resin binder are used in a dry state, and a liquid developer in which toner components are dispersed in an insulating liquid.
In a liquid developer, toner particles are dispersed in oil in an insulating liquid, thereby making it possible to form smaller particle sizes as compared to a dry developer. Therefore, high-quality printouts can be obtained surpassing offset printing, so that the liquid developer is suitable for commercial printing applications. In the recent years, with increasing demands for speeding up, the lowering of viscosities in the liquid developers has been desired.
In addition, in the recent years, with the increased awareness of environmental friendliness, an insulating liquid having a low volatility has been used as a dispersion medium for a liquid developer.
Patent Publication 1 discloses a recording material containing at least a poly-alpha-olefin as a non-aqueous dispersion medium, for the purpose of controlling, reducing etc. the generation of steam of a solvent in an electrophotographic liquid developer, clogging of nozzles due to evaporation of a solvent in an oily inkjet ink, odor or toxicity in a Magic Marker ink, odor of an insulating liquid in an electronic ink, or the like.
Patent Publication 2 discloses a liquid developer characterized in that supernatant of a liquid in which a colorant is dispersed in a carrier solvent has a transmittance of 60% or more over the entire region of wavelengths between 250 nm and 350 nm, for the purpose of providing a liquid developer in which excellent printouts are obtained with high reproducibility even after repeats of printouts, and a petroleum-based hydrocarbon solvent has been used as a preferred insulating solvent.
Patent Publication 1: Japanese Patent Laid-Open No. 2005-10528
Patent Publication 2: Japanese Patent Laid-Open No. Hei-11-202563